Here is a quote from Rusty Shovel on his Nomadic rack.  The side racks may also add support against flexing because they tie into the foot peg brackets.

Re: Touratech Side Racks & Nomadic Top Rack Combo -- Install
« Reply #2 on: December 02, 2014, 02:41:49 pm »
Quote
The rear rack has remained solid.  I've taken the entire setup camping with a pair of fully loaded Wolfman Expedition bags, 2 gallon Rotopax, and my trusty walmart lunchbox on the tail rack (probably about 50 lbs) with no issues.

I take that back, I have had one issue.  I went to Big Bend with a fully fueled Rotopax and after a couple of days of hard riding I noticed that two of the bracket mounts for the Rotopax holder had broken.  I'm gonna call Rotopax and see if they'll send me some beefier brackets.

The racks have all been solid.  If fact, the Touratech rack has been forced into roll cage duty and has done well.

I'll get some photos of the broken brackets up soon.

I wanted to chime in to be clear that, when paired with Touratech side racks, most of the weight on the rear rack is supported by the passenger foot peg brackets, so the tank threads don't handle much of the the load.  That said, I've never read any complaints that the *plastic* (usually said with a sneer) actually failed; only the subframe bolts, which can be replaced with beefier versions mentioned in this thread.

I don't think the tank *ever* fails.  I think it's actually made of adamantium.

I've never heard of the metal threads failing, which mean it will probably soon just so the universe can show me how little I know (again).

Also, my apologies to Rotopax, it wasn't their mount that broke.  It was the Wolfman Pawnee Plate's brackets that snapped.  Wolfman said it's sending me beefier brackets soon.